446 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



ever be contemplated in Port Madoc channel such 

 analyses would, of course, be necessary. 



There does not seem to be any suitable place where 

 such cleansing tanks could be erected in the upper parts 

 of the harbour. The Glaslyn river, to the east of the 

 lock-gates, is polluted by the sewer discharging near 

 Britannia Foundry (No. 4), as well as by the sewage 

 that doubtless flows occasionally down the little brook 

 opening into the river here. There appear to be 

 difficulties in the way of constructing any works on or 

 near the Ballast Bank, though these would not be 

 insuperable to an engineer if cost did not matter. Then, 

 because of the imperfect flushing of the river, between 

 the harbour and Borth, with flood-tide water from the 

 open sea, this part of the channel is also unsuitable. 

 There remains only the plan of putting up a tank lower 

 down than Borth. 



Mussels occur here and there in the channel near 

 the rocks called Gareg Goch and Careg Cnwc, and it was 

 suggested by Dr. Bulstrode that the seriously polluted 

 shellfish from the upper part of the harbour might be 

 transplanted to this part of the channel. This general 

 removal of mussels from the harbour and redeposition in 

 the seaward part of the channel could, of course, be 

 carried out by an organisation similar to that set up at 

 Morecambe some years ago, and it would lead not only 

 to a certain amount of purification of the shellfish, but 

 also to an increase in growth. But even here there is 

 risk of pollution in such circumstances as floods in the 

 upper part of the river during low neap tides. Thus the 

 analysis made on 11th April, 1913, showed that the 

 mussels at Gareg Goch were polluted to a less degree 

 than those in the harbour; this was at a time when there 

 was little fresh water in the river. But on 21st April 



